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Date: Thu, 29 Jan 2015 12:34:50 -0600
From: Timur Tabi <timur@codeaurora.org>
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To: Ard Biesheuvel <ard.biesheuvel@linaro.org>
CC: Catalin Marinas <catalin.marinas@arm.com>,
        Mark Rutland <Mark.Rutland@arm.com>, Rob Herring <robh@kernel.org>,
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        "linux-acpi@vger.kernel.org" <linux-acpi@vger.kernel.org>,
        Arnd Bergmann <arnd@arndb.de>,
        "linaro-acpi@lists.linaro.org" <linaro-acpi@lists.linaro.org>,
        Marc Zyngier <Marc.Zyngier@arm.com>, Will Deacon <Will.Deacon@arm.com>,
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	<linux-arm-kernel@lists.infradead.org>,
        Jason Cooper <jason@lakedaemon.net>
Subject: Re: [Linaro-acpi] [PATCH v7 04/17] ARM64 / ACPI: Introduce early_param
 for "acpi" and pass acpi=force to enable ACPI
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On 01/29/2015 12:28 PM, Ard Biesheuvel wrote:
> The UEFI stub in the kernel uses the DTB file format (FDT) to pass
> information about the UEFI memory map and system table to the kernel.
> It does so even if there is no device tree that describes the
> platform. In this case, the file only contains a /chosen DT node, and
> nothing else, and it is up to the kernel to figure out that it can ask
> UEFI for a set of ACPI tables that it can use instead to configure the
> system. Otherwise, the /chosen node properties are added to a device
> tree that contains the full platform description.
>
> The problem is that we have to decide how to distinguish a
> conventional device tree DTB from a DTB that only exists to
> communicate the UEFI entry points.

Ah, that's exactly what I'm seeing.  The UEFI stub in our kernel 
generates a DTB, and therefore I always need to put acpi=force on our 
kernel command line.

-- 
Qualcomm Innovation Center, Inc.
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